Bicycle battery charger and speedometer circuit

ABSTRACT

A circuit that receives signals from a dynamo and provides signals for charging a battery and indicating bicycle speed. The circuit includes a first switching circuit adapted to receive the dynamo signals and provide first signals for charging the battery; and a second switching circuit adapted to receive the dynamo signals and provide second signals for indicating bicycle speed. If the dynamo outputs periodic signals, the first signals may correspond to one of the half periods of the periodic signals (e.g., the positive half periods), and the second signals may correspond to the other half periods (e.g., the negative half periods) of the periodic signals.

BACKGROUND OF THE INVENTION

The present invention is directed to bicycles and, more particularly, toa circuit that receives signals from a dynamo and provides signals forcharging a battery and indicating bicycle speed.

Bicycles often are equipped with dynamos for powering headlights andother types of lights. Contemporary bicycles, however, are equipped notonly with such lights but also with actuators for operating electricallydriven shifters, actuators for adjusting the dampening force of anelectrically driven suspension, indicator backlights for cyclecomputers, and the like. Such equipment will be referred to below as“electrically driven units”, and they also receive their power from thedynamo. These electrically driven units begin operating unstably whentheir electric drive voltage falls below a specific level, so someaccommodation must be made for supplying stable electric drive voltageto them. In late-model bicycles, a dynamo charges a secondary batterywhich, in turn, powers the electrically driven units. Because stableelectric drive voltage is needed to energize such electrically drivenunits in the above-described manner, the present inventor has alreadydevised and proposed an apparatus that allows the charging voltage to bedetected and a stabilized charging voltage to be obtained throughappropriate switching of the dynamo output.

Speedometers are sometimes mounted on bicycles. Such speedometersoperate with speed detection signals such as signals from a sensor thatsenses signals from a magnet mounted to the bicycle wheel. A techniquefor retrieving speed detection signals from a dynamo output is disclosedin JP (Kokai) 7-229909. However, when the dynamo output is switched in acontrolled manner in order to control the charging voltage, the voltagedrop varies significantly because of the presence of a load resistance,an impedance or inductance in the dynamo, or the like. The switchingalso induces substantial disruptions in the output waveform of thedynamo. Low-pass filters and other circuits are needed in order toobtain a speed detection signal from a signal whose waveform is markedlydisrupted in this manner, thus increasing the size and cost of thedevice.

SUMMARY OF THE INVENTION

The present invention is directed to a comparatively simple circuit thatreceives signals from a dynamo and provides stable signals for charginga battery and indicating bicycle speed. In one embodiment of the presentinvention, such a circuit includes a first switching circuit adapted toreceive the dynamo signals and provide first signals for charging thebattery; and a second switching circuit adapted to receive the dynamosignals and provide second signals for indicating bicycle speed. In amore specific embodiment adapted for use with a dynamo that outputsperiodic signals, the first signals may correspond to one of the halfperiods of the periodic signals (e.g., the positive half periods), andthe second signals may correspond to the other half periods (e.g., thenegative half periods) of the periodic signals. This may be accomplishedusing diode elements in the first and second switching circuits. A thirdswitching circuit may be provided for selectively inhibiting the outputof the first signals to the battery until the circuit is sufficientlystable, and a pulse signal circuit may be provided for producing pulsesignals from the second signals to facilitate the operation of thespeedometer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual schematic diagram of a particular embodiment of abattery charging and speed indicating circuit according to the presentinvention;

FIG. 2 is a detailed schematic diagram of the circuit shown in FIG. 1;and

FIGS. 3(A) and 3(B) are diagrams of waveforms output by the secondswitching circuit and the dynamo, respectively.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a conceptual schematic diagram of a particular embodiment of abattery charging and speed indicating circuit according to the presentinvention. The circuit comprises a dynamo 1 (generator), a firstrectifying circuit 2 (first switching circuit), a second rectifyingcircuit 6 (second switching circuit), a secondary battery 3 (e.g., acapacitor) as a power supply for electrically driven units, and a switch5 (third switching circuit) disposed between the dynamo 1 and thesecondary battery 3. The circuit further comprises and a Schmitt circuit7 coupled to the second rectifying circuit 6 for waveform shaping.

The dynamo 1 may, for example, be a hub dynamo built into the hub of thebicycle front wheel, and it is provided with an internal impedance R andan internal inductance L. The rectifying circuit 2 contains diodes orthe like to rectify the alternating-current voltage output by the dynamo1 and to provide the secondary battery 3 with the resulting positive ornegative (e.g., positive) half-periods. The switch 5 containscapacitors, transistors or the like for selectively inhibiting thecommunication of the signals from rectifying circuit 2 to battery 3. Thesecond rectifying circuit 6 contains diodes or the like to rectify thealternating-current voltage output by the dynamo 1 and to provide thespeedometer circuit (not shown) with the resulting positive or negative(e.g., negative) half-periods as a speed detection signal. The Schmittcircuit 7 receives the output of the second rectifying circuit 6 andoutputs a pulse signal such as the one shown in FIG. 1 to facilitate theoperation of the speedometer, which usually comprises a microcomputer.

The signal waveforms of the various components of the circuit shown inFIG. 1 will now be described. The switch 5 is open or closed inaccordance with the charging voltage of the secondary battery 3. Theswitching operation causes the load resistance to change abruptly, thusmarkedly varying the voltage drop due to the effect of the internalimpedance R or internal inductance L of the dynamo 1. The dynamo outputwaveform is thereby disrupted violently as shown in FIG. 1. In thiscase, the output waveform is disrupted only during the positivehalf-periods because charging occurs only during these half-periods. Inconventional devices a low-pass filter or other circuit is needed toderive a speed detection signal from such a disrupted output waveform.In view of this, the present embodiment is configured such that thesecond rectifying circuit 6 retrieves the negative half-periods of theoutput provided by the dynamo 1, and the signal waveform is shaped toprovide a pulse signal for speed detection. As shown in FIG. 1, thespeed detection signal can be readily formed without waveformdisruption.

FIG. 2 is a detailed schematic diagram of the circuit shown in FIG. 1.In the circuit shown in FIG. 2, the positive and negative parts of thewaveforms output by the dynamo 1 are the opposite of those produced bythe circuit shown in FIG. 1.

As shown in FIG. 2, dynamo 1 is coupled with a first capacitor C1, asecond capacitor C2, a first diode D1, and a second diode D2. In thiscircuit, the first and second capacitors C1, C2 and the first and seconddiodes D1, D2 constitute a voltage-doubling rectifier circuit. The firstcapacitor C1 is charged during the positive half-cycle of dynamo 1output, and during the subsequent negative half-cycle the secondcapacitor C2 is charged with voltage equal to the voltage generated bydynamo 1 plus the charged voltage of the first capacitor C1. Thus, thesecond capacitor C2 can acquire high charged voltage at low speed. Thesecond capacitor C2 functions as a power supply for driving first andthird field-effect transistors FET1 and FET3, described later.

A third diode D3 serving as a rectifier circuit is coupled with dynamo1, and the output of this third diode D3 is coupled, via the firstfield-effect transistor (hereinafter simply “transistor”) FET1, to athird capacitor C3 serving as a rechargeable battery. The gate of firsttransistor FET1 is coupled, via a first resistor R1, to the secondcapacitor C2. In this circuit, the third diode D3 allows the thirdcapacitor C3 to be charged, via first transistor FET1, with the outputof dynamo 1 only during the negative half-cycle thereof. As is wellknown for such transistors, if the potential at the gate of firsttransistor FET1 is higher than that at the source by more than apredetermined level (2 V, for example), first transistor FET1 switcheson. Since the voltage of the second capacitor C2 is applied to the gateof the first transistor FET1, the applied voltage is sufficiently higheven under the low speed condition described earlier, the firsttransistor FET1 is stabilized in the ON state, and the third capacitorC3 charging operation is stabilized.

The second transistor FET2, third transistor FET3 (corresponding toswitch 5 in FIG. 1) and lamp 4 are connected in series to dynamo 1.Diode D5, shown connected in parallel with second transistor FET2, anddiode D4, shown connected in parallel with third transistor FET3, areparasitic diodes for the respective transistors FET2, FET3. The gate ofthe second transistor FET2 is coupled via a second resistor R2 to thesecond capacitor C2, and the gate of the third transistor FET3 iscoupled to a control circuit 10. A third resistor R3 is also connectedin parallel with the gate of third transistor FET3.

With this circuit arrangement, the gate potential of the firsttransistor FET1 can be controlled by control circuit 10 to controlcharging of the third capacitor C3, and the gate potential of the thirdtransistor FET3 can be controlled according to the charged voltage ofthe third capacitor C3 to control on/off operation of the thirdtransistor FET3. By switching off the second transistor FET2 togetherwith the third transistor FET3, the lamp 4 can be extinguishedcompletely.

Diode D6 is connected to the output of dynamo 1 to rectify thealternating-current voltage output by the dynamo 1 and to output thepositive half-periods of the dynamo signals. The Schmitt circuit 7receives the output of diode D6 and outputs a pulse signal such as theone shown in FIG. 1 as a speed detection signal to facilitate theoperation of the speedometer, which usually comprises a microcomputer(not shown). Thus, the speed detection signal is produced from thepositive half-periods of the generator output.

The operation of the circuit will now be described. It is assumed thatall capacitors are initially empty. First, during the positivehalf-cycle of the output of dynamo 1, current flows over path (1):

(1): dynamo→D1→C1→dynamo

This results in charging the first capacitor C1. The voltage across thefirst capacitor C1 reaches approximately the dynamo output peak voltageof 0.6 V.

During the subsequent negative half-cycle current flows in reverse overpath (2):

(2):dynamo→C1→D2→C2→D5→dynamo

This results in charging the second capacitor C2. The current suppliedto the second capacitor C2 is equal to the current from dynamo 1 pluscurrent from the charged first capacitor C1. Thus, the second capacitorC2 can be charged adequately even at low speed. When the voltage acrossthe second capacitor C2 reaches {(voltage across C3)+(ON trigger voltagefor gate of FET1)}, the first transistor FET1 turns on. The secondtransistor FET2 turns on as well. Thus, current now flows also over path(3):

(3): dynamo→D3ΘFET1→C3→FET2→dynamo

This initiates charging of the third capacitor C3. With thisarrangement, the third capacitor C3 can be stably charged to relativelyhigh voltage during the negative half-cycle of dynamo output only.Furthermore, as the voltage applied to the gate of the first transistorFET1 can be stabilized by the second capacitor C2, the ON state of thefirst transistor FET1 can be stabilized.

At this time the voltage across the third capacitor C3 is not adequatefor driving other electrically powered units in a stable manner. Thus,the voltage applied to the gate of the third transistor FET3 iscontrolled by the control circuit 10 so that the third transistor FET3remains off. During the positive half-cycle, the first capacitor C1 ischarged by means of current flowing over path (1):

(1): dynamo→D1→C1→dynamo

as described above, and the lamp 4 is lit by means of current flowingover path (4):

(4): dynamo→FET2→D4→lamp→dynamo.

During the subsequent negative half-cycle, the second capacitor C2 andthird capacitor C3 are charged by means of current flowing over path(2):

(2): dynamo→C1→D2→C2→FET2→dynamo

and current flowing over path (3):

(3): dynamo→D3→FET1→C3→FET2→dynamo.

The above operation by means of current flowing over paths (1) and (4)during the positive half-cycle of dynamo output and operation by meansof current flowing over paths (2) and (3) during the negativehalf-cycle, are performed repeatedly.

When electric current flows along paths (1) and (4), the dynamo outputof positive half-periods is extracted by the diode D6, and the waveformis shaped by the Schmitt circuit 7. The pulse signal generated by theSchmitt circuit 7 is used as a speed detection signal. During positivehalf-periods, the load varies only slightly because it consists of thelamp 4 alone. Thus, a speed detection signal can be provided duringthose positive half-periods in a simple and accurate manner.

FIG. 3(b) shows the waveform of dynamo output in this case, and FIG.3(a) shows the waveform of the diode D6 (which is also the waveform ofthe voltage applied to the lamp 4). As will be apparent from thedrawings, the lamp 4 is lit during the positive half-cycle of dynamooutput, while the rechargeable battery (capacitor C3) is charged duringthe negative half-cycle. In FIG. 3(b), the positive peak voltage V1 islower than the negative peak voltage V2; this is due to a drop involtage in the dynamo resulting from the lamp load. The third capacitorC3 is repeatedly recharged in this manner, and when the voltage acrossthe third capacitor C3 reaches a level sufficient to drive otherdevices, the third transistor FET3 is turned on by the control circuit10. This causes current to flow over path(5);

(5) dynamo→lamp→FET3→FET2→dynamo

so that the lamp lights. In this state the lamp is lit notintermittently, but continuously during both the positive and negativehalf-cycles of dynamo output. The lamp 4 can be extinguished completelyby switching off the second transistor FET2 in addition to the thirdtransistor FET3.

While the above is a description of various embodiments of the presentinvention, further modifications may be employed without departing fromthe spirit and scope of the present invention. For example, the size,shape, location or orientation of the various components may be changedas desired. Components that are shown directly connected or contactingeach other may have intermediate structures disposed between them. Thefunctions of one element may be performed by two, and vice versa. It isnot necessary for all advantages to be present in a particularembodiment at the same time. Every feature which is unique from theprior art, alone or in combination with other features, also should beconsidered a separate description of further inventions by theapplicant, including the structural and/or functional concepts embodiedby such feature(s). Thus, the scope of the invention should not belimited by the specific structures disclosed or the apparent initialfocus on a particular structure or feature.

1. A circuit that receives periodic signals from a an alternatingcurrent dynamo and provides signals for charging a battery andindicating bicycle speed, wherein the circuit comprises: a firstswitching circuit adapted to receive the dynamo signals and providefirst signals for charging the battery; and a second switching circuitadapted to receive the dynamo signals and provide second signals forindicating bicycle speed; and a third switching circuit that selectivelyinhibits the output of the first signals to the battery.
 2. The circuitaccording to claim 1 further comprising a pulse signal circuit forproviding pulse signals from the second signals.
 3. The circuitaccording to claim 2 wherein the pulse signal circuit comprises aSchmitt circuit.
 4. The circuit according to claim 1 further comprisinga third switching circuit that selectively inhibits the output of thefirst signals to the battery.
 5. The circuit according to claim 4 1wherein the third switching circuit comprises a transistor.
 6. Thecircuit according to claim 1 wherein the first switching circuitcomprises a first diode element, and wherein the second switchingcircuit comprises a second diode element.
 7. The circuit according toclaim 1 wherein the dynamo signals are periodic signals, A circuit thatreceives periodic signals from an alternating current dynamo andprovides signals for charging a battery and indicating bicycle speed,wherein the circuit comprises: a first switching circuit adapted toreceive the dynamo signals and provide first signals for charging thebattery; and a second switching circuit adapted to receive the dynamosignals and provide second signals for indicating bicycle speed; whereina second signal is not provided at a same time as a first signal isprovided; and wherein the first signals correspond to one of the halfperiods of the periodic signals, and wherein the second signalscorrespond to the other half periods of the periodic signals.
 8. Thecircuit according to claim 2 7 wherein the first signals correspond topositive half periods of the periodic signals, and wherein the secondsignals correspond to negative half periods of the periodic signals. 9.The circuit according to claim 7 wherein the first switching circuitcomprises a first diode element, and wherein the second switchingcircuit comprises a second diode element.
 10. The circuit according toclaim 9 further comprising a pulse signal circuit for providing pulsesignals from the second signals.
 11. The circuit according to claim 10wherein the pulse signal circuit comprises a Schmitt circuit.
 12. Thecircuit according to claim 11 further comprising a third switchingcircuit that selectively inhibits the output of the first signals to thebattery.
 13. The circuit according to claim 12 wherein the thirdswitching circuit comprises a transistor.
 14. The circuit according toclaim 13 wherein the first signals correspond to positive half periodsof the periodic signals, and wherein the second signals correspond tonegative half periods of the periodic signals.
 15. The circuit accordingto claim 1 further comprising a power supply charged by the dynamo forcontrolling operation of the third switching circuit.
 16. The circuitaccording to claim 15 wherein the power supply comprises a capacitor.17. The circuit according to claim 7 further comprising a pulse signalcircuit for providing pulse signals from the second signals.
 18. Thecircuit according to claim 17 wherein the pulse signal circuit comprisesa Schmitt circuit.
 19. The circuit according to claim 7 furthercomprising a third switching circuit that selectively inhibits theoutput of the first signals to the battery.
 20. The circuit according toclaim 19 wherein the third switching circuit comprises a transistor. 21.The circuit according to claim 19 further comprising a power supplycharged by the dynamo for controlling operation of the third switchingcircuit.
 22. The circuit according to claim 21 wherein the power supplycomprises a capacitor.
 23. The circuit according to claim 22 wherein thethird switching circuit comprises a transistor.
 24. The circuitaccording to claim 7 wherein the first switching circuit comprises afirst diode element, and wherein the second switching circuit comprisesa second diode element.
 25. The circuit according to claim 7 wherein thefirst signals consist essentially of one of the half periods of theperiodic signals, and wherein the second signals consist essentially ofthe other half periods of the periodic signals.
 26. The circuitaccording to claim 7 wherein the first signals are mutually exclusivefrom the second signals.
 27. The circuit according to claim 7 wherein apolarity of the first signals is opposite a polarity of the secondsignals.